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21824 = 261131
BaseRepresentation
bin101010101000000
31002221022
411111000
51144244
6245012
7120425
oct52500
932838
1021824
1115440
1210768
139c1a
147d4c
1566ee
hex5540

21824 has 28 divisors (see below), whose sum is σ = 48768. Its totient is φ = 9600.

The previous prime is 21821. The next prime is 21839. The reversal of 21824 is 42812.

It is a nude number because it is divisible by every one of its digits.

It is a plaindrome in base 15.

It is a nialpdrome in base 4 and base 16.

It is a zygodrome in base 4 and base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 689 + ... + 719.

221824 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24384).

21824 is an abundant number, since it is smaller than the sum of its proper divisors (26944).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21824 is a wasteful number, since it uses less digits than its factorization.

21824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54 (or 44 counting only the distinct ones).

The product of its digits is 128, while the sum is 17.

The square root of 21824 is about 147.7294825010. The cubic root of 21824 is about 27.9454721113.

Adding to 21824 its product of digits (128), we get a cube (21952 = 283).

It can be divided in two parts, 218 and 24, that added together give a palindrome (242).

The spelling of 21824 in words is "twenty-one thousand, eight hundred twenty-four".

Divisors: 1 2 4 8 11 16 22 31 32 44 62 64 88 124 176 248 341 352 496 682 704 992 1364 1984 2728 5456 10912 21824